Frost lifting a barn skirt slab and binding slider doors

[vtsnowedin]

An old contractor once told me you could build a road out of horse feathers if you could just keep them dry.
Up here in New England we put four feet of granular clean ,sand gravel, crushed gravel or crushed rock under a paved surface to keep it from heaving when frozen and below that we shape and drain the subgrade so that water is directed away from the roadbed as much as possible. Underdrain pipes six feet below edge of pavement are standard in any earth cut.
Your slab will probably settle back pretty much to where it was as your frost is probably not too deep and hasn't been there for many weeks. Next summer you can try adding side drainage that gets the water three feet below the bottom of the slab and drains off to daylight well away from the building. If that doesn't work you can either install doors that can function with the slab frost jacked up or redo the slab. If you redo the slab cut your subgrade down a uniform two feet and drain away the lower corners of the subgrade. then backfill with sand and crusher run that meets spec. (Less then 12% silt in the sand portion). Two eight inch layers of sand and one eight inch layer of crushed gravel or crushed rock and it will never move in Virginia again baring an earthquake.

 

[CobyRupert]

The internet says (thus it must be true!) that water expands ("heaves") its volume about 9-10% when it freezes (lifting the soil that it is saturating). = Drainage! (or putting a bigger covering over it)

 

[vtsnowedin]

The internet says (thus it must be true!) that water expands ("heaves") its volume about 9-10% when it freezes (lifting the soil that it is saturating). = Drainage! (or putting a bigger covering over it)

It can be much more then 10%. Ever notice when you put a straw in a glass of water how the water level is higher then the level in the glass? It is caused by the surface tension of the water. The smaller the diameter of the straw the higher the water will go. In a fine soil like loam or clay the small spaces between the soil particles act like straws, very small straws, that suck up water from below and keep adding it to the ice lens that is forming as the cold strips away heat from the water. If enough water is present and the soil fine enough you can get heaves that are two feet or more higher then they are in summer.
Granular clean material on the other hand has straws too big to pull water up so the frost heave can't begin to grow until the road is frozen all the way down through the sand and gravel to the top of the water in the subgrade.

 

[DFB]

When I lived in Maine the area I was in was mostly clay soil. I had never seen soil in my life that would heave like that. It would lift and swell just like a sponge during the wet seasons and then when it would drain and go back it would leave voids that if you stepped on it would collapse down. Coming from a 3 generation family of sand gravel mining and processing that my grandfather had built up I was amazed at the soil behavior. And of course with tillage if the timing wasn't right when it dried it was just clumped up in balls hard like concrete! With a lot of new house construction around there they would only dig down 3 or 4 feet at most to set footings and actually fill in and build up around the exposed foundation walls with drawn in sand fill...expensive operation!

Travel a lot of secondary roads here in New England you almost never fail to come across a large bump especially in late Winter or Spring most usually a large rock under the blacktop pushing its way up from the frost

 

[s219]

The more I think about it, drainage would have to be a factor here. The barn is on a gentle downhill slope. Grade slopes away from barn on the sides and back, but there's no way to get around the fact that the natural grade slopes toward the front of the barn overall. I did proper sloping of the skirt and driveway of 1/4" per foot going out 10' from the door opening, and that seems to divert surface water just fine (could see it flow away from barn even during a downpour). But surely dampness/moisture continues to work towards the skirt through the soil below.

What I will probably do is dig a trench around the front of the barn and skirt and go down 12-16" or so to get below our typical frost level, fill with #57 gravel, and then carry the trench around to the swale on the sides of the barn until it meets up with grade. That will make both the top of the skirt and the underlying fill act as somewhat of a high spot compared to the trench.

 

[mjcountrybumpkin]

Just curious , how much snow is on the roof. If a decent amount could it be flexing the structure downward ?

 

[s219]

Just curious , how much snow is on the roof. If a decent amount could it be flexing the structure downward ?

There was about 8" of snow compacted by 1" of sleet on the roof for a while (it's mostly all melted now due to sun and warmer temps). Certainly possible the added weight has settled the pole footings a little more (barn was only built last May/June). I will take a look at all the poles to see if I can tell if they settled any, relative to the floor slab. Each pole had some expansion strip placed around it so that it wouldn't stress or crack the floor slab if there was movement.

 

[DFB]

Ha know what some amateur volunteers did this weekend?

That public building I had previously mentioned that has a big issue with getting the doors to fully open outward because of slab lift, was to be used for public restrooms during a winter festival being held this weekend and the building inspector had made his ruling that only a limited number of people could be in the building at any one time given the bottleneck the narrow door openings would create.

So my buddy told me last night one of the hubby's of one of volunteers took an 41/2 angle grinder and ground the concrete walk down in front of the doors so they would fully open...now my buddy says a day later the door doesn't open all the way again!